• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.539-539
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• 2012

전북대학교 고온플라즈마 응용연구센터는 교육과학기술부 기초연구사업 중 고가연구장비 구축사업의 일환으로, 고 엔탈피, 초음속 유동 환경을 모사하여, 항공우주, 군사기기, 핵융합 분야 등의 고온 재료 개발을 위한 기초 연구 장치로써, 0.4MW급 플라즈마 풍동 장치를 구축하고 있다. 0.4MW 플라즈마 풍동 장치의 플라즈마 발생부는 DC 전원 공급장치와 디스크 형태의 양극과 음극 사이에 동일 형태의 간극을 삽입한 0.4MW급 분절형 아크 플라즈마 토치로 구성되었으며, 토치에서 발생된 아크 플라즈마는 노즐을 통과하며 마하 2~4의 초음속을 나타내도록 설계 제작되었다. 시험 챔버는 노즐에서 나온 초음속 플라즈마의 특성 및 재료 시험을 위한 3차원 이송식 기판이 장착되어 있으며, 고 엔탈피 유동을 관측하기 위한 광학창을 구비하였다. 시험 챔버 하류에는 유동 안정을 위한 디퓨저(diffuser)가 설치되어 있으며, 디퓨저(diffuser)로부터 배출되는 고온가스는 열교환기를 통해 냉각된 후 진공펌프를 통해 대기로 배출되게 된다. 장치의 압력조절을 위하여 $1,000m^3/min$의 용량의 진공펌프 시스템이 설치될 예정이며 가스공급장치, 냉각수 공급장치, 디퓨져, 열교환기는 1MW급 용량으로 설계 제작되었다. 본 장치는 400kW의 전원 공급, 15 g/s의 공기유량 주입 시 약 13 MJ/kg의 고엔탈피를 가진, mach 2~4의 초음속 유동을 나타내는 것을 특징으로 한다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.95.2-95.2
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• 2012

고온형 SOFC의 개발에 있어 스택의 신뢰성을 확보하는데 가장 중요한 핵심기술은 스택 구성요소 사이를 접합하는데 필요한 고온형 밀봉재의 개발이다. SOFC 스택에서의 밀봉재는 고체전해질과 접속자 사이에서 음극에 공급되는 연료가스와 양극에 공급되는 공기가 서로 혼합되는 것을 방지하는 역할은 물론 기계적으로 취약한 단전지의 보호 및 스택전체 구조물의 구조적 일체성(Structural integrity)을 부여하는데 주목적이 있다. 현재 기체 기밀성을 유지하기 위한 밀봉재는 크게 유리 및 결정화 유리계, mica및 mica/유리복합재료, 유리/충전재 복합재료 등이 사용되고 있으나 다수의 단위전지로 구성되는 스택 구성에서 스택의 열기계적 안정성 및 장기수명을 보장하기 위해서는 본 연구에서 개발하고자 하는 복합밀봉재가 가장 적합할 것으로 예상되고 있다. 본 연구에서는 SiO-B2O3-RO계에 BaO, SrO를 일정비율로 첨가하여 제작된 유리 frit을 열처리하여 물리화학적 물성변화를 검토하였으며, $750^{\circ}C$ 이하의 연화점을 갖는 유리를 기지상으로 하고 세라믹 보강재를 첨가한 고온형 복합밀봉재를 개발하고 그 물리화학적 안정성, 열기계적 안정성 및 밀봉 특성을 평가하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.53-61
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• 2021

This paper is a preliminary study for the development of a drone for inspection inside a boiler in a thermal power plant, which is a high-temperature environment, and validated whether the drone can fly normally through a high-temperature environment simulation using AirSim. In a high-temperature flight environment, the aerodynamic characteristics of the air density and viscosity are different from room temperature, and the flight performance of the drone is also changed accordingly. Therefore, in order to confirm the change of the aerodynamic characteristics of the propeller according to the temperature change, the propeller analysis and thrust test through JBLADE, and the operation characteristics prediction through the electric propulsion system performance prediction model were performed. In addition, the analysis and performance prediction results were applied to AirSim for simulation, and the aircraft redesigned through the analysis of the results. As a result of the redesign, it was confirmed that about 65% of the maximum power used before the redesign was reduced to 52% to obtain the necessary thrust when hovering in an environment of 80℃.

• Composites Research
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• v.30 no.2
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• pp.116-125
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• 2017

The purpose of this study is to develop silicon carbide fiber showing an excellent mechanical properties under highly oxidative conditions at high temperature. Polycarbosilane(PCS) as a preceramic precursor was used for making the SiC fiber. PCS fiber was taken by melt spinning method followed by melting the PCS at $300{\sim}350^{\circ}C$ in N2 gas. The Curing of PCS fiber was carried out in air oxygen chamber, prior to high temperature pyrolysis. Degree of cure was calculated by characteristic peak's ratio of Si-H to $Si-CH_3$ in FT-IR spectra before and after curing of PCS fiber. The properties of SiC fiber was affected greatly by the degree of cure. The SiC fiber produced by controlling fiber tension during heat treatment showed good properties. The SiC fiber exposed to $1000^{\circ}C$ at air from 1 min. up to maximum 50 hrs showed around 60% reduction in tensile strength. We found that large amount of carbon content on the fiber surface after long-term exposure has resulted in lower tensile strength.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.2
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• pp.155-164
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• 2014

Carbon-fiber-reinforced plastic (CFRP) composites are increasingly being used in a variety of industry applications, such as aircraft, automobiles, and ships because of their high specific stiffness and high specific strength. Aircraft are exposed to high temperatures and high humidity for a long duration during flights. CFRP materials of the aircraft can absorb water, which could decrease the adhesion strength of these materials and cause their volumes to change with variation in internal stress. Therefore, it is necessary to estimate the characteristics of CFRP composites under actual conditions from the viewpoint of aircraft safety. In this study air-coupled ultrasonic testing (ACUT) was applied to the evaluation of water absorption properties of CFRP composites. CFRP specimens were fabricated and immersed in distilled water at $75^{\circ}C$ for 30, 60, and 120 days, after which their ultrasonic images were obtained by ACUT. The water absorption properties were determined by quantitatively analyzing the changes in ultrasonic signals. Further, shear strength was applied to the specimens to verify the changes in their mechanical properties for water absorption.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.316-321
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• 2013

This study was carried out to analyze heat transfer characteristics and heat flow through air-inflated double layer PO film with thermal resistance method. The experiments was conducted in the laboratory controlled air temperature between 258.0 K and 278.0 K. The experimental materials were made up two layers PO film and an inflated-air layer. The thickness of air-inflated layer was fixed at 3 types of 110, 175, 225 mm. The electrical circuit analogy for heat transfer by conduction, radiation and convection was introduced. Experimental data shows that the dominant thermal resistance in heat transfer through the air-inflated double layer film was convection. Calculation errors were 1.1~18.5 W for heat flow. In result, the method of thermal resistance could be introduced for analysis of heat flow characteristics through air-inflated double layer film.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.70-76
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• 1992

Ignition of hydrogen-air premixed gas in the vicinity of a hot surface has been investigated. Especially multistep reaction model was compared with a single reaction model. It was found that the multistep model with 48 step elementary chemical reactions produced a phenomenologically reasonable trend in ignition delays. The ignition d(2lays increase as the mixture becomes either fuel-rich or fuel-lean with a minimum near the stoichiometric value. The minimum surface temperature has been deduced by extrapolating predicted ignition delays. It was in quite good agreement with the experimental data.

• Fire Science and Engineering
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• v.28 no.4
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• pp.8-13
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• 2014

In order to improve safety for hydrogen network infrastructure, the ignition temperature by hot wire was investigated for different hydrogen compositions in pipelines. The result shows that minimum temperature for ignition decreased with decreasing hydrogen composition. The minimum temperature was confirmed at a hydrogen composition of approximately 10 vol.%. The one of the reasons is supposed that buoyancy force should generate the convection of gas mixture. It was also found that humidity had a little effect on ignition temperature, flame temperature.

• Solar Energy
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• v.12 no.1
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• pp.95-102
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• 1992

A small scale solar collector system composed of a Fresnel lens of $0.5m^2$ area as a solar concentrator and a compact fluidized-bed solar receiver was developed. Performance and temperature distribution in the fluidized bed receiver were measured using SiC for particles and air for working fluid. The maximum gas temperature was attained up to 1250K at this moment. In this study, energy efficiency achieved by the present experiment was high for the small scale solar collector system and compact receiver.

• Journal of the KSME
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• v.31 no.7
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• pp.652-656
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• 1991

일반적으로 로켓 추진기관이라고 하면 외부로부터의 산소 공급없이, 추진제라고 불리는 물질이 연소할 때 발생하는 고온 고압의 연소가스를 고속으로 노즐로 통과시켜 추력을 얻는기관을 말 한다. 연소는 산소와의 화합반응이 급격히 일어날 때 일어나는 현상이므로 외부로부터 산소공 급이 없다는 것은, 추진제 자체에서 산소공급이 가능하다는 것을 의미한다. 즉, 추진제는 그 자 체가 흔히 말하는 연료성분과 산소를 공급할 수 있는 산소화합물을 같이 묶어둔 물질이어야 한다. 그러나 지구를 둘러싸고 있는 대기에는 산소가 20%나 포함되어 있으며, 이 무궁무진한 산소를 이용하지 않는다는 것은 여러 면에서 손실임을 쉽게 알 수 있을 것이다. 그럼에도 불구 하고 이를 이용하지 못하고 있었음은 그 나름대로의 어려움이 있었기 때문일 것이다. 그러나 인간의 노력과 연구로 불가능했던 많은 사실도 가능하게 된 것이 헤아릴 수 없이 많아지고 있음 또한 주지의 사실이다. 로켓 추진기관 분야에서도 순수 연료 성분만을 로켓에 탑재하고 산소는 흡입되는 대기중의 것을 이용하자는 것이 새로운 연구분야로 각광을 얻고 있으며, 실제로 이러한 방법이 실용화되고 있다. 이와 같이 흡입공기를 산소원으로 하는 추진기관을 총칭 램제트 추진 기관이라고 한다.